Re: [Log4cplus-devel] Socket close hangs

[Václav Z. <vha...@gm...>]

On 09/18/2013 09:51 AM, palladin wrote:
> Dear log4cplus devels,
> log4cplus 1.1.1-RC4
> <https://sourceforge.net/projects/log4cplus/files/log4cplus-stable/1.1.1/>
> Linux version 2.6.32-279.22.1.37.0.el6.x86_64 (abuild@noriko) (gcc
> version 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC) )
> 
> My application has hung after it have used log4cplus::helpers::Socket
> from  log4cplus::helpers::ServerSocket::accept,e.g.
> log4cplus::helpers::Socket clientSocket = mServerSocket.accept();
> clientSocket was put into log4cplus::thread::AbstractThread worker.
> Client socket was used in AbstractThread like Socket::read - this is
> blocking call and the root of issue.
> 
> Then my application worked for some time  and at the end I did
> clientSocket.close() from main thread.
> Due to the fact that log4cplus::helpers::Socket::read is blocking call -
> my application has hung on AbstractThread::join call.
> 
> I would like to suggest a fiew fixes to this issue:
> 1) add non-blocking stuff to log4cplus::helpers::Socket - select or poll.
> 2) add to log4cplus::helpers::Socket interface system call shutdown( man
> 2 shutdown ).
Closing a socket from one thread when the socket is blocked on any
operation in another thread is AFAIK very unportable.

This could be solved in a way similar to how I have done
ServerSocket::accept(), which is indeed using poll() to wait for either
an incoming connection or some data arriving to a special interrupt pipe.

Also, these helpers are there to help log4cplus. They are not there to
be used as public networking framework/API, so fixing this has a low
priority for me right now. OTOH, I am open to accepting reasonable patches.

-- 
VZ